Brinell Hardness Test

A standardized test of metal hardness. It is made by indenting the smooth surface of the metal under test by mean of a hardened steel ball (usually 10mm in diameter) by subjecting it to a pressure or load of 300 kilograms for a soft metal and 3000 kilograms for a hard metal. For very hard materials, a 2mm diameter diamond sphere is used.
By means of a lens, the diameter of the indentation in the metal surface is measured, and this is used as a means of calculating comparative hardness numbers - Brinell hardness number.